Government climate scientist James Hansen this week warned that Earth's atmosphere already has too much of the greenhouse gas, carbon dioxide, and that that will result in irreversible changes unless CO2 concentrations are reduced.

HANSEN: "We really have reached a point of a planetary emergency. And it's because there are tipping points in the climate system, which we are very close to and which, if we pass, the dynamics of the system can take over, so the momentum of the system will carry you to very large changes, which are out of your control, if you pass the tipping points."

Hansen heads the Goddard Institute of Space Studies, which is part of the U.S. space agency, NASA.

His comments came 20 years to the day after he first told a U.S. Senate committee that global warming is a real threat. Two decades ago there was widespread skepticism that the planet really was getting warmer, and that human activities were to blame. But Hansen said then that according to his research, it was 99 percent certain that warmer temperatures were being caused by a build-up of carbon dioxide emissions and other human-caused pollution in the earth's atmosphere.

Twenty years later, Hansen returned to Congress and also spoke at the National Press Club. He said that some of the latest evidence of climate change can be seen in the Arctic Ocean, where, he says, we've already reached one tipping point.

HANSEN: "The sea ice 30 years ago was about eight million square kilometers at the end of the melting season. In 2007 it was down to just over four million. We know that we're going to lose that sea ice because there's enough warming in the pipeline that this process is going to cause us to lose all that sea ice."

Scientists measure atmospheric gases in parts per million, or ppm. The atmosphere now has about 385 parts per million of carbon dioxide, the best-known greenhouse gas.

HANSEN: "If we want to stop the sea ice from melting, we've got to go back to 325 to 350 ppm of CO2."

NASA climate scientist James Hansen, speaking Monday at the National Press Club here in Washington.

Sea ice isn't the only thing affected by climate change.

A new study published Thursday concludes that forest plants are heading for higher and cooler locations in the face of rising average temperatures. French researchers writing in the journal Science studied where different species were located and they found that the plants' optimum locations were almost 30 meters per decade higher in elevation, meaning they were migrating to cooler environments. The study used data going back more than a century.

The World Conservation Union estimates that at least one-third of all known frog and other amphibian species are threatened with extinction. In fact, zoos and aquariums around the world have declared 2008 the Year of the Frog to highlight the threat. Habitat loss is one reason, but researchers think a fungal infection is also to blame. As we hear from reporter Rebecca Williams, researchers are working on a possible solution.

WILLIAMS: A disease caused by something called chytrid fungus is sweeping through frogs. When the disease moves through a frog population it can wipe out 80 percent of the entire population. Scientists have been rushing to find something that might help.

Reid Harris is a biologist at James Madison University. He says he's discovered there are friendly bacteria that live on some types of frogs. And they can kill the fungus.

HARRIS: "It does seem like the pathogen moves in this predictable wave, so you might be able to get out in front of that wave sort of like a fire line."

WILLIAMS: Harris says it might be possible to give wild frogs extra doses of the bacteria to fight off the fungus. But first they have to make sure there won't be side effects. For The Environment Report I'm Rebecca Williams.

Support for the Environment Report comes from the Joyce Foundation, the Gaylord and Dorothy Donnelley Foundation, and the Consumers Energy Foundation. You can contact them at feedback@EnvironmentReport.org.

Looking back over hundreds of millions of years, scientists have found evidence of periodic mass extinctions, when as much as 95 percent of all life on earth was wiped out. But they are still looking for what causes these cataclysmic events. Reporter Eric Libby says the answer might lie in the oceans.

LIBBY: Geologist Shanan Peters has always been interested in paleontology, specifically life in the ancient oceans.

PETERS: "I grew up in a small town in Ohio. In fact, all of the rocks in the Ohio, almost all of the rocks, were deposited in a shallow sea. Here we are in the middle of the continent, 800 kilometers from the nearest ocean with marine rocks everywhere. So, I was interested from a very early age as to what the significance of the coming and going of these oceans might be."

LIBBY: At the University of Wisconsin, he has researched the effects of the rise and fall of oceans and found a connection between changes in ocean level and mass extinctions.

Although species are constantly going extinct, there have been times when the number of populations dying off rises sharply. There have been an estimated 23 episodes of such mass extinctions in the history of life on earth — including the disappearance of the dinosaurs. While some of these can be explained because they coincide in the geological record with meteorite impact craters or layers of volcanic ash, others remain a mystery. But Peters found a commonality among all of them: changing ocean levels and environments.

PETERS: "Many of the extinctions we see in the marine animal fossil record and more importantly which animals are more affected than others during a particular event, are very well predicted by contractions in two important types of marine environments. And the two environments are carbonates and siliciclastics."

LIBBY: Carbonate environments are the tourist beaches with white sands and clear water. They tend to have few nutrients in the water so you see organisms like coral at the bottom. The other beaches, siliciclastics, have brown sands and murky water. They are full of sediment and support creatures like snails and clams. As the ocean levels change over time, the balance of these two environments shifts, and that, in turn, determines which marine animals live or die. Peters says this ebb and flow also affects life on land.

PETERS: "About 80 million years ago during the Cretaceous period when the dinosaurs where thriving, many areas of the North American continent were flooded by shallow continental seaways. That ocean drained at the end of the Cretaceous and many of the animals that used to live in those environments were strongly affected. But the loss of that sea would have also affected climate and precipitation throughout the entire continent."

LIBBY: Peters' work links the fluctuations of species in the fossil record with geologic events that can alter ocean levels, like global warming, erosion, and volcanic eruptions.

Although Peters looked at changes in the distant past, he says there are lessons for today. Humans are contributing to changes in marine environments. Agricultural waste water carries sediments into the ocean, upsetting the balance between the carbonate and siliciclastic environments. Global warming is shrinking the polar ice sheets, which contributes to a gradual rise in sea level.

PETERS: "Frankly for the marine world a sea level rise isn't necessarily a bad thing. The bad part of sea-level rise really comes down to the human factor. We've constructed society in such a way to be very sensitive to the climate and sea-level status quo. And any change in that status quo will be quite important for us."

LIBBY: Peters' findings offer scientists a more robust, predictive indicator for the success of life both on land and in the sea, linking waves of mass extinction to waves of ocean height. This is Eric Libby in Washington.

Time again for our Website of the Week, when we showcase interesting and innovative online destinations.

This week we feature a website that harnesses the unused power of a million computers around the world to help solve complex scientific problems for the benefit of some of the world's poorest people.

The site uses a technology called grid computing. The idea is to break big problems down into small pieces. Then, lots of computers connected to the Internet can each work on a part of the problem.

There are other grid computing projects on the Web, but Stan Litow says WorldCommunityGrid.org is different.

LITOW: "The power on World Community Grid is used purely for humanitarian purposes — cancer research, research on dengue fever, rice DNA — all kinds of public purposes. So that's one thing. But the second thing is, it's a permanent source that can serve humanitarian needs year in and year out."

Litow is a vice president of IBM Corporation, which funds the program.

World Community Grid has been online for about two years now. To participate, it only takes a few minutes to sign up. And each participant can choose what project they want to work on.

LITOW: "You actually decide, and then on WorldCommunityGrid.org's site, you can actually track how much work your power has done — individual calculations — and you can see the progress of the research day by day."

Users download software for Windows, Mac, or Linux. You don't need a huge hard drive or a fast Internet connection. And it doesn't interfere with your other computer activities.

Members in more than 200 countries and territories are participating.

LITOW: "And the research projects are also worldwide. The muscular dystrophy research project comes from France. The climate modeling, from Africa. And the rice DNA study, to try to address the world food crisis, comes from Washington state, right here in the U.S."

Scientists working on projects with a humanitarian goal can apply, and proposals approved by the advisory board get free computing time that's equivalent to a session on a supercomputer. IBM's Stan Litow says one condition is that they must agree to share their findings broadly with the entire community.

Do some good by donating your spare computing resources — you're not using them anyway — at WorldCommunityGrid.org, or get the link to this and more than 200 other Websites of the Week from our site, voanews.com/ourworld.

A study published this month highlights the difficulty many women in developing countries face getting tested for cervical cancer.

At one time it was one of the leading cancer killers of women around the world. And as health reporter Rose Hoban reports, it was hard to detect until it was too late.

HOBAN: But that changed in the 1950s with the widespread introduction of the Pap test. In countries where the Pap test is widely used, cervical cancer deaths have plunged by as much as 90 percent.

But results of a new survey show that in too many countries, too few women are screened for cervical cancer. Dr. Ziad Obermeyer from the University of Washington examined the data. OBERMEYER: "These data that we used actually came from a set of surveys that were carried out by the United Nations in 2002 and 2003, and specifically by the World Health Organization."

HOBAN: Surveyors went door to door in dozens of developing countries to ask women if they had ever had a pelvic exam or a Pap test.

OBERMEYER: "If you look at whether or not the respondents have ever had a pelvic exam, that number was at about 70 percent in developed countries and 45 percent in the developing world. In some of these countries the rates were just staggeringly low. So, if you look at rates in Ethiopia, Bangladesh, or Burma (Myanmar) 90 percent of women had never had a pelvic exam. And only one percent of women had been effectively screened."

HOBAN: Obermeyer says these numbers are consistent with what's already known — that most of the world's deaths from cervical cancer take place in developing countries. The World Health Organization estimates there are about half a million cases worldwide every year, and about half those women die from the disease.

Obermeyer says changing this screening rate will be challenging.

OBERMEYER: "I think that the one bottom line from our paper, which is highlighted by the fact that there is such a variety of screening practices, is that there is not going to be a one-size-fits-all strategy that will work for every country."

HOBAN: Obermeyer says some of these countries would be good places for use of the new cervical cancer vaccine. But the vaccine is still quite expensive and still, women need to be checked with an effective cervical cancer test after several years. He says in some places there are cultural obstacles to providing this test for women. Other places are more open to doing more screening, but they need better laboratory facilities and more health care personnel.

Obermeyer's paper is published in the online journal PLoS Medicine. I'm Rose Hoban.

A new study puts the number of surgeries performed globally each year at just over 234 million, with an increasing number of procedures now being done in developing countries. As the number of operations goes up, experts say the number of surgical complications does, too. The World Health Organization hopes to reduce complications with an operating room checklist. VOA's Jessica Berman explains.

BERMAN: International public health experts estimate at least one million patients die each year as a result of surgical complications, deaths that might be avoided through proper procedures.

Atul Gawande is a surgeon at Harvard University in Boston, Massachusetts and lead author of the first international study of surgery and surgical practices.

GAWANDE: "People are living longer. And so you see in the parts of the world like Asia, the Middle East, South America that they are all places where now cancers are in the top 10 as killers, road traffic accidents in the top five. And so what we've seen around the world is an explosion in the use of surgical care."

Gawande led a study in which investigators analyzed the surgical data of 56 countries.

In the United States and other developed countries, surgical complications led to death in less than one-percent of cases. In developing countries, the number of deaths following surgery ranged between five and 10 percent.

Gawande heads the WHO's Surgery Saves initiative, an effort to reduce the number of surgical complications worldwide. The centerpiece of the initiative is a checklist for operating room personnel.

Gawande says the checklist is intended for doctors and nurses in all countries to make sure they follow all of the necessary steps in the operating room to ensure patient health.

For example, Gawande says infection following surgery is a leading cause of death that can be prevented by giving a patient an antibiotic an hour before an operation.

GAWANDE: "What's the likelihood that we will give the antibiotic on time? Globally, it is a less than one third chance. And even in the best countries, it is missed about one third of the time."

Gawande says he's been using the checklist in the operating room and has caught some missed steps. But he says there's some resistance among surgeons who wonder whether taking the extra time is worth it.

GAWANDE: "But talk to patients and they are puzzled. Pilots use a checklist before they take off. You mean my surgeon isn't using a checklist already? And I think it's sort of a no-brainer on one level. These things work, they help and they help ensure that teams work as effectively as possible."

The study on worldwide surgeries is published on line in the medical journal The Lancet. Jessica Berman, VOA News, Washington.

And finally today ... Wild lion populations can generally tolerate a certain level of parasites and disease. But new research shows that extreme climate conditions — such as severe droughts — can cause infection rates to skyrocket, resulting in mass die-offs. Véronique LaCapra reports.

LaCAPRA: The savannas of Tanzania are home to as many as half of the world's lions. University of Minnesota ecology professor Craig Packer has been studying lions in Tanzania's Serengeti National Park for the past 30 years. He was there in 1994, when, inexplicably, the animals started dying.

PACKER: "We estimate that about 1,000 lions died over a relatively short period of time. It was unprecedented: over the previous 30 years nothing had been seen anything like it."

LaCAPRA: Then, in 2001, it happened again.

PACKER: "In the nearby Ngorogoro crater, we saw another die-off, just like the one in the Serengeti seven years earlier."

LaCAPRA: By analyzing the lions' blood, Packer and his colleagues found that the two die-offs seemed to be triggered by outbreaks of canine distemper virus, a disease that usually affects domestic dogs.

PACKER: "Distemper is a carnivore equivalent of measles. The nice thing for us about measles is that our bodies produce an immunological response to the virus so that we can only ever be infected once.

Distemper has the same effect in the bodies of carnivores, and so at any age whenever an animal is exposed to distemper, the animal — if it survives the infection — has antibodies and is therefore immune to further cases of distemper."

LaCAPRA: According to Packer, it's relatively common for lions to get the disease. In the Serengeti, he has seen distemper outbreaks about every six or seven years, usually with no symptoms.

PACKER: "Most of the time it's harmless, you just find out that the animals were exposed because you see their antibodies in their blood, but you think back to the date when that virus must have struck, and there was no obvious sign of illness."

LaCAPRA: But in 1994 and 2001, about a third of the animals that got infected, died. What had turned a normally benign outbreak into a devastating epidemic?

PACKER: "In 1993, in the Serengeti, we had the first in a series of pretty serious droughts that we've been having out in east Africa."

LaCAPRA: The drought was especially brutal for a common prey of lions, the Cape buffalo. For the lions, the drought-weakened buffalo made an easy catch: they ate almost nothing else. But the unexpected feast came at a high price.

PACKER: "These buffalo were infested with ticks."

LaCAPRA: And with them, came a tick-borne parasite, called babesia. Animals in the Serengeti are always exposed to ticks and babesia, which at its worst can cause malaria-like symptoms, anemia, and hemorrhaging. In a normal year, Packer says, lions can tolerate the parasite.

PACKER: "But the drought of 1993 led to an unprecedented increase in the lions' exposure to babesia."

LaCAPRA: And then, as soon as the drought ended, distemper struck the babesia-ridden lions. The combination proved fatal.

PACKER: "Getting canine distemper is like having a short sharp bout of AIDS."

LaCAPRA: Like AIDS, the distemper virus attacks the immune system, weakening the body's defense against other infections.

PACKER: "So the virus kind of liberated the tick-borne disease so that it could be far more destructive than it would have otherwise been."

LaCAPRA: Although the lion populations were able to recover from the die-offs within a few years, Packer thinks deadly epidemics will become more frequent if climate change continues.

PACKER: "What we're seeing now is much greater variability in the weather than we'd ever seen in the past. Most climate change models do predict a greater variance in weather. Any given year might be more likely to have a flood or a drought. And that's definitely been the experience in my 36 years in working out here."

LaCAPRA: Packer adds that extreme droughts and floods are likely to continue unleashing new, potentially synergistic combinations of diseases, which could be more deadly together than they would be on their own. His research is published in the journal PloS ONE. I'm Véronique LaCapra.

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Rob Sivak edited the show. Eva Nenicka is the technical director. And this is Art Chimes, inviting you to join us online at voanews.com/ourworld or on your radio next Saturday and Sunday as we check out the latest in science and technology ... in Our World.